The present invention generally relates to methods, systems, and devices for controlling lasers, and is particularly useful for controlling pulse energies of excimer lasers during laser eye surgery.
Known laser eye surgery procedures generally employ an ultraviolet or infrared laser to remove a microscopic layer of stromal tissue from the cornea of the eye so as to alter the refractive characteristics of the eye. The laser typically removes a selected shape of the corneal tissue, often to correct refractive errors of the eye. Ultraviolet laser ablation can result in photo-decomposition of the corneal tissue, but generally does not cause significant thermal damage to adjacent and underlying tissues of the eye. The irradiated molecules are broken into smaller volatile fragments photochemically, directly breaking the intermolecular bonds.
Laser ablation procedures can remove the targeted stroma of the cornea to change the cornea's contour for varying purposes, such as for correcting myopia, hyperopia, astigmatism, and the like. Control over the distribution of ablation energy across the cornea may be provided by a variety of systems and methods, including the use of ablatable masks, fixed and movable apertures, controlled scanning systems, eye movement tracking mechanisms, and the like. In known laser systems, the laser beam often comprises a series of discrete pulses of laser light energy, with the total shape and amount of tissue removed being determined by the shape, size, location, and/or number of laser energy pulses including in a pattern of pulses directed onto the cornea. A variety of algorithms may be used to calculate the pattern of laser pulses used to reshape the cornea so as to correct a refractive error of the eye. Known systems make use of a variety of forms of lasers and/or laser energy to effect the correction, including infrared lasers, ultraviolet lasers, femtosecond lasers, frequency multiplied solid-state lasers, and the like.
Known corneal correction treatment methods have generally been successful in correcting standard vision errors including myopia, hyperopia, astigmatism, and the like. More recently, highly accurate measurements of defects or irregularities in the optical system of the eye have been made widely available. Wavefront measurements of the eye identify irregular aberrations of the eye with sufficient accuracy to allow a customized ablation pattern to be developed. By customizing the refractive procedure to the specific defects of a patient's eye, it is often possible to correct irregular minor aberrations reliably and repeatedly, often providing visual acuities after treatment of better than 20/20.
As with many advances, still further improvements in laser eye surgery methods would be desirable. For example, as the accuracy of wavefront aberration measurements and general laser surgical techniques has increased, the benefits of more and more precise control over the distribution of laser energy over the eye has also grown. Work in connection with the present invention has determined that improvements in devices, systems, and methods for controlling the energies of light pulses generated by the laser may increase the accuracy of a refractive procedure.
Excimer lasers have been used for a number of years in a variety of industrial processes, and while the laser pulse energy control systems derived from industrial excimer laser controllers and/or previously developed for refractive resculpting have helped allow the rapid growth in laser eye surgery to date, additional improvements may benefit from a recognition of the differences between the uses of excimer lasers in industrial processing and their use in laser eye surgery systems. For example, many laser eye surgery systems employ optical components which move during the surgical procedure so as to distribute the laser energy across the cornea. The firing rate of the laser for the individual pulses may vary somewhat to accommodate this movement, and the like. Additionally, the total time during a refractive procedure may be significantly shorter than the timeframes in which industrial excimer lasers run. These and other differences between the use and structures of laser eye surgery systems and industrial laser devices indicate that benefits may be available by providing improved and/or specialized devices, systems, and methods for controlling lasers for use in laser eye surgery.
In light of the above, it would generally be beneficial to provide improved devices, systems, and methods for controlling lasers, particularly for controlling excimer lasers used in laser eye surgery systems. It would be helpful if these improved techniques could enhance the accuracy and reliability of laser eye surgery without significantly increasing the complexity or cost of the treatments, and ideally by taking advantage of components which have already been developed and are now included in many laser eye surgery systems.